alt Hacker NewsIm curious what exactly you ask here. I consider myself to be a decent engineer (for practical purposes) but without a CS degree, and I might likely have not passed that question.
I know compilers can do some crazy optimizations but wouldn't have guessed it'll transform something from O(n) to O(1). Having said that, I dont still feel this has too much relevance to my actual job for the most part. Such performance knowledge seems to be very abstracted away from actual programming by database systems, or managed offerings like spark and snowflake, that unless you intend to work on these systems this knowledge isn't that useful (being aware they happen can be though, for sure).
Replies
My interview aims to assess whether the candidate understands that the dependency of each iteration on the previous one prevents effective utilization of a superscalar processor, knows the ways to overcome that, and whether the compiler is able to optimize that automatically, and if so when it absolutely cannot and why.
I generally focus more on sum of arbitrary data, but I used to also ask about a formulaic sum (linear to constant time) as an example of something a compiler is unlikely to do.
My thinking is that I expect good engineers to be able to do those optimizations themselves rather than rely on compilers.
He thinks it makes him look clever, or more likely subtlety wants people to think "wow, this guy thinks something is obvious when Matt Godbolt found it surprising".
This kind of question is entirely useless in an interview. It's just a random bit of trivia that either a potential hire happen to have come across, or happens to remember from math class.